Cell permeable peptide inhibitors of protein kinase (PKA) sub-cellular localization will be designed to identify signal transduction pathways in cardiac myocytes that are specific for type I and type II isoforms of PKA. This will provide entry points for drug discovery efforts aimed at down-regulating specific isoforms of PKA that are associated with heart disease. First generation peptides that bind selectivity to type I and type II regulatory subunit isoforms of PKA have been designed. In phase I of this proposal we will optimize the peptides for cell permeability by attaching carrier molecules that facilitate membrane transport and evaluate their ability to interfere with PKA sub-cellular localization in an isoform-selective manner in adult rat cardiac myocytes. This research will establish proof of concept for a phase II project to evaluate the selective interference of these peptides in PKA-regulated ion channels that are known to be hyperphosphorylated and altered in heart failure and disease. Drug discovery efforts will be initiated for specific isoforms of PKA that alter ion channel function in heart disease. Optimized peptides in phase I of this project will be valuable tools for probing PKA-isoform-specific functions in many cell types and will be made available for use by the scientific research community.